Direct Visualization of Regurgitant Orifice by CMR Reveals Differential Asymmetry According to Etiology of Mitral Regurgitation

OBJECTIVES This study sought to characterize the shape of regurgitant orifice area (ROA) and mitral apparatus in various forms of mitral regurgitation (MR) by cardiac magnetic resonance (CMR). BACKGROUND ROA is an accepted parameter of MR severity. However, there are little data on the shape of the ROA in various forms of MR. METHODS Direct assessment of ROA was performed with a 1.5-T CMR scanner using a breath-hold fast imaging with steady-state free precession. The regurgitant orifice shape and the anatomy of the mitral valve apparatus including mitral annulus, mitral leaflet angles, and mitral valve tenting area were assessed. RESULTS We studied 74 patients. MR severity was mild in 39%, moderate in 27%, and moderate-to-severe or severe in 34%. Mitral valve pathology was degenerative in 26%, prolapse in 22%, flail in 33%, and functional in 19%. For all patients, ROA correlated significantly with regurgitant fraction (r = 0.80, p < 0.001). The ROA shape index as expressed by the ratio of the larger length to the smaller length was a median of 2.04 (interquartile range [IQR]: 1.49 to 3.08) over all patients. CMR revealed significant asymmetry of the ROA geometry in functional MR 3.91 (IQR: 2.79 to 4.84) compared with prolapse 2.14 (IQR: 1.80 to 3.04), flail 2.20 (IQR: 1.69 to 2.91), and degenerative MR 1.24 (IQR: 1.09 to 1.57), all p < 0.01. The assessment of mitral valve geometry demonstrated that patients with functional MR had significantly increased leaflet angles, mitral valve tenting area, and mitral annulus area (all p < 0.05). Of note, the orifice shape index correlated with increasing leaflet angles in patients with functional MR (r = 0.68, p = 0.005). CONCLUSIONS Direct assessment of ROA by CMR revealed significant asymmetry of ROA in various forms of MR, particularly in patients with functional MR. The slitlike appearance in functional MR correlates with a distended mitral apparatus. (J Am Coll Cardiol Img 2011;4:1088-96) c 2011 by the American College of Cardiology Foundation